Help Checking my numbers, and a bit of Direction...

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RacinNdrummin

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Sep 18, 2012
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Ive been wavering around in choosing a turbo for my P7100 6.9(7.0) IDI currently under construction. I was looking at similar displacements and what turbo's were working good on those engines and had pretty decided on a 471/475 for this setup, running as a single to help keep the bottom end together, That was until recently when I started putting numbers together and comparing dyno info from the past.

Previous Dyno runs have put the IDI air consumption right at 5.2-5.3lbs per HP at HP peak, which is significantly lower than most engines this size, or in otherwords, it likes its air. These were determined by boost seen at HP peak on two separate engines, Running the same cam, and achieving the same HP/TQ rpm peaks, though different levels of power. The first engine was a small CC pump, 7.3/ZF5, intercooled, S362, It did 477wtq@2200rpm and 235whp@2800rpm, Boost at HP peak was 17-18lbs. The other engine was a 6.9 with a bore (7.0), more fuel ,ZF5, same IC, S363, It did 685wtq@2200rpm and 365whp@2800rpm, Boost at HP peak was 35psi. This puts both in the 5.2-5.3 range.

So now onto my current build... I am after 600whp, I have the fuel to do it with no issue, but the air is what is hanging me up. As said above, Im going to run this a single (At least to start) and Im looking to spin this thing to keep cylinder pressures down, instead of a 2800rpm hp peak, Im looking more into the 3400 range (or more) with full fueling to 4K. Using the numbers above, it looks like im going to need 113lbs of air to make 600whp happen, and it will require 55psi of boost at 3400rpm to achieve that. That leaves me with something significantly bigger than a 471/475... I would have to run an S480, and even then, it doesn't look like it would be good for a single unless I wanted HP peak a little higher..

No onto the other end of the equation, do to the fact that its IDI and achieving a bit more of a complete burn over the crank angle, we tend to see about 2 2.6-2.8hp/cc ratio at HP peak (2800). Bringing the HP peak higher is going to want to maintain that ratio, even when you include the parasitic loss of increased power output. Being that less exhaust energy is going to be used to drive the turbine, and Im not going to have dynamic timing control, how would one go about sizing the turbine to this particular set of parameters? I can do things like control injection duration through playing with the pop-pressure, that is something an IDI responds real well to do to our injector style, and I will have even more wiggle room due to the pump, but I don't know what I should look at as far as a turbine wheel to go with the 80mm compressor. Im wondering if it wouldn't be good to size the wheel big (96mm) and step down to a 1.0 T4 exhaust housing, or what....

Any help from the guru's would be much appreciated...
 
I am no "guru" but here is my take. My first question in an educated response is what is your intended usage and expectations. The IDI is a good engine I own one and a cummins as well. However the IDI requires a LOT of air to make power. The next thing would be what transmission are you going to use. If your are building a 4r100 what stall would you prefer? You would need a big stall to light a S471 or larger in any sort of reasonable time frame. You are talking atmospheric turbo size numbers in an engine that probably processes air less efficiently than a cummins 12v. To really maximize the package you are working with WHILE maintaining drive-ability you are in the same boat as 12v owners which is high rpm screaming monster with lack luster bottom end response or make the move towards twins. I am also assuming that you will be lowering the compression somewhat in order to handle the increased boost your engine will see which further compounds the issue. You didn't mention head work or camshaft which could change the tone of my response entirely as well. Good luck with the build I would love to see a screamer of a IDI that wasn't saddled with the injection limitations that international handicapped them with.
 
Its intended use is a Toy. Im purposefully building a higher RPM setup in hoping the reduced cylinder pressures up higher will make the bottom end live a little longer. Setup is as followed:

85 6.9 block bored .040"
Balanced Rotating assembly
Main Girdle/Studs
IDIT Rods (Same forgings as the 7.3psd Rods)
18:1 (.050" shaved pistons, Tricoated)
9/16" ARP Head Studs @190ft/lbs
O-ringed Block
Comp 910's shimmed .030"
Smith Bro's Pushrods
"Performance" valve job
Cam (103ICL, 210*@.050int, 210*@.050exh, 112lobe sep, .416" lift)
Head flow- 185cfm@.400"int, 150cfm@.400"exh
*might do a bit of port work while I have the heads off*
P7100 300cc@4000rpm... to start..

Will be running through my ZF5 until it blows, and will then swap a ZF6 in.

Depending on its manners, it will probably get daily driven, but its towing days are over and its basically just my hotrod. The engine above already has 3500 miles on it, and the top end is apart to fix a HG, Upgrade to the 9/16 studs, Oring the block, and drop the new cam in.
 
The cam above is experimental, I had it ground up to test. The cam that is coming out of the engine is 111ICL, 180*/195*@.050, same lift... The specs above I came up with from knowing how the "bigger" cam that NMB2 and I ran (The cam from the dyno numbers above) acted, and how my current cam acts, and what I wanted out of the new grind.
 
When did the power start to fall off with the old cam? That new cam has the potential to make power towards the 4500rpm range. The head flow could be better if you wanted to see power that high though. Really 200cfm+ on the intake side and equal attention to the exhaust would be a better match to that cam if you could pull it off. That's a great looking build you got going on for an IDI.
 
gman99 said:
When did the power start to fall off with the old cam? That new cam has the potential to make power towards the 4500rpm range. The head flow could be better if you wanted to see power that high though. Really 200cfm+ on the intake side and equal attention to the exhaust would be a better match to that cam if you could pull it off. That's a great looking build you got going on for an IDI.
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I don't know, I haven't dyno'd the setup with the current cam, and realistically, I didn't develop it for higher RPM power, just a smooth powerband and a bit of dynamic (very little) compression bleed for the stock compression guys... Matt at Gearhead gave me some pointers, and I gave it a bit of my own take, its a true stage 1 cam, and makes the IDI a less peaky, more turbo friendly engine... The Cam above in the dyno numbers wanted to continue out well past 2800, but due to the nature of the DB pump fueling (worse curve than a VE cummins), it just couldn't hold, That being said, this new cam isn't far off. Its lift is a bit less because I wanted to take a bit of stress off the stamped rockers and there was only a 3cfm gain from .400 to .500 lift on the intake, and I added a bit more duration on the intake, and retarded it a bit, but otherwise its pretty similar, Just tuning really.

Beyond that, I have a set of ported heads that I couldn't use because one had several cracks, its been sitting at the machine shop waiting flow testing for about 8 months now, they just havent gotten around to it, maybe I need to bust some balls, because I could port another head to replace the cracked one... This is a pic I posted in the fab thread....

picture.php


Im sure it would do over 200cfm... The exhaust side Im less worried about because of the combustion characteristics... If I run a tight exhaust side with this cam, I should be fine as it will keep the pressures copacetic with the cold side, or am I misreading things? I already have a feeling im going to have to tinker with this a bit, provided the engine structure holds up...
 
I just went through two sets of heads on a dodge 360 that were cracked out, I feel your pain. This first set I had many hours of port work into as well.

It sure looks like you have room to put a larger valve on the intake side. Yes I agree that your exhaust flow is good. The only reason I said anything about it was due to the straight pattern of the cam. Out of curiosity did you run into any overlap issues with the opening and closing points selected, and was that the reason for the straight pattern?

If you want to inquire I know there is a technique called spray welding where the head is preheated to 700 plus degrees and a nickel weld is "sprayed". I have never used it I only know that it is an option. I have used nickel rods to weld cast iron with good results so I have to imagine preheated and cooled properly it could be an option for you depending on the cracks.
 
Are you married to the idea of a single? A small set of compounds would be good at giving a decent amount of boost pressure without too much fuel. Also, might want to look into the Aurora 5000 if you can fit it under the hood. Big exducer on the compressor for the size, light frame, etc.
 
gman99 said:
I just went through two sets of heads on a dodge 360 that were cracked out, I feel your pain. This first set I had many hours of port work into as well.

It sure looks like you have room to put a larger valve on the intake side. Yes I agree that your exhaust flow is good. The only reason I said anything about it was due to the straight pattern of the cam. Out of curiosity did you run into any overlap issues with the opening and closing points selected, and was that the reason for the straight pattern?

If you want to inquire I know there is a technique called spray welding where the head is preheated to 700 plus degrees and a nickel weld is "sprayed". I have never used it I only know that it is an option. I have used nickel rods to weld cast iron with good results so I have to imagine preheated and cooled properly it could be an option for you depending on the cracks.
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Yes, there is significant overlap with this cam, and the reality behind that, is when I had it ground, I was going compounds (HX35 and S471, and later Eaton M112/S471) on my 190cc DB pump, and when I was weighing pressure ratios, it seemed like I had a bit of room to grow. Its still negative as far as events at .050" go (-4.8*), but I do realize that a lot happens with pressure under .050". I am hoping to gate the turbo and keep things as close to 1:1 as possible (hopefully under where it counts) and that is the only reason I am still running this grind. The whole idea between the equal lobes (And I lied above, I looked at the cam card, and its 212*), was that I need a bit more open time on the intake side because of the air demands of the IDI. Cummins cams are significantly biased towards the exhaust side, but the air requirements are pretty damn efficient. The cam in the dyno above had a slight exhaust bias (209/215), but I didn't like how early the exhaust opened and I figured with that being the case, and needing the extra air, I was going to "steal" a little from the exhaust side, and give it to the intake, hence the 212/212.

Beyond that, Ive looked a bit into welding the heads, but I wanted to get flow numbers first before I sink money into the boat anchors, and beyond that, it might be cheaper (in my time) to just do another head...
 
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JQmile said:
Are you married to the idea of a single? A small set of compounds would be good at giving a decent amount of boost pressure without too much fuel. Also, might want to look into the Aurora 5000 if you can fit it under the hood. Big exducer on the compressor for the size, light frame, etc.
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Jason, I im not totally set on a single, but I would like to see how it reacts with one first.... If its too soft, I will consider an S360 or 363 in the mix...
 
I have to say after doing my own research I am pretty certain that you would be hard pressed to reach your goal with a "streetable" single. I think it could happen with some trial and error, but you my friend are in rarefied air with your setup. A goal of 500 seems realistic for a single in your application. But if a 363 on its own didn't crack 400hp I really just don't see 600 happening very easily on a single. The lbs a minute calculations put you at an S480 at minimum and ideally a S482 to make a solid 600 as you already noted.

Your idea of a 360 or 363 to keep costs reasonable I think is a good one. Then cut out some fenderwell and go to town with a twin setup. A GTX-4294R 71T DBB or even a GTX-4202R 76T DBB could be a good single for you. They are pretty proud of them though. I would email jose at forced inductions your end goal, lbs min requirements and see what he had to say.

I admire what it takes to push ahead with a unique combo such as this and wish you the best of luck with it.
 
RacinNdrummin said:
Jason, I im not totally set on a single, but I would like to see how it reacts with one first.... If its too soft, I will consider an S360 or 363 in the mix...
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Are you sure that the P7100 pump won't help in the HP per Air department? I assume the rest of your builds may be based on having a not-P7100 pump...:Cheer:
 
JQmile said:
Are you sure that the P7100 pump won't help in the HP per Air department? I assume the rest of your builds may be based on having a not-P7100 pump...:Cheer:
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That's one of those crystal ball questions I just cant answer...

Ill put it this way though, Because its odd trying to compare a bunch of stuff I read in the DI builds. It seems to me that other V8 diesels, particularly the PSD stuff, that HP/CC of fuel is significantly less than what we are seeing out of our IDI's. Now that could be because of differences in factory calibration specs, or that we milk more power out of the fuel we do have. That may correspond over to the air demands as well. Maybe the fact that the IDI has such a high HP/CC ratio is directly tied to how low the hp per Lb/min is, and its directly related to the rate of burn. IDI starts very slow but catches up and often surpasses the combustion rate of DI, an maybe that's do to the air charge and the atomization at the exit of the precup, all in relation to crank angle? I know that my 190cc DB pump was severely limited by 2500lb pop pressures, and I was seeing a lot less boost than I should have, it had to have been cutting 50cc right off the top, but the truck was snappy and clean, especially down low. The nice part about the P-pump is the injection pressures Ill be able to get away with. I plan on starting with a 3000psi pop-pressure, and a .050" nozzle (DI equivalent to a 5x.020), and with that rate of injection, its possible that I might be able to make my numbers with less air. We will just have to see.
 
The head flow, cam and P7100 all put together should net you more power up top by a significant margin. My IDI starts tapering at 2800 or so. I have to believe your combo should add at least 1000rpm to the drop off point. Fuel quantity is no longer an issue what so ever in your case. The pump will put out enough to either drown the fire or blow the bottom out. The real question is will the 5.3hp to lbs/min ratio stay unchanged for the remainder of the powerband if you move it up that much. In all reality it "should" get better, but that's just speculation. If you made the same 685 torque at 3800rpm you would be right at 495hp though...

Since you already had it running for 3500 miles I am assuming that you already have a decent existing turbo. Why not try that one back out for a while so you can get a feel for the fueling and rpm curves of the engine? You wouldn't have to spend money trying to match a turbo to an unknown hp and torque curve that could be far different than anticipated. Changing too many variables at once can lead to alot of headaches if problems arise. Especially in an odd combo such as yours.

I am trying to think of this as what I would do on my own project. I usually like to do things step by step and if not I go over things ten times and over think the variables too much.

I would love to see a dyno or street video when its done that's for sure!
 
gman99 said:
The head flow, cam and P7100 all put together should net you more power up top by a significant margin. My IDI starts tapering at 2800 or so. I have to believe your combo should add at least 1000rpm to the drop off point. Fuel quantity is no longer an issue what so ever in your case. The pump will put out enough to either drown the fire or blow the bottom out. The real question is will the 5.3hp to lbs/min ratio stay unchanged for the remainder of the powerband if you move it up that much. In all reality it "should" get better, but that's just speculation. If you made the same 685 torque at 3800rpm you would be right at 495hp though...

Since you already had it running for 3500 miles I am assuming that you already have a decent existing turbo. Why not try that one back out for a while so you can get a feel for the fueling and rpm curves of the engine? You wouldn't have to spend money trying to match a turbo to an unknown hp and torque curve that could be far different than anticipated. Changing too many variables at once can lead to alot of headaches if problems arise. Especially in an odd combo such as yours.

I am trying to think of this as what I would do on my own project. I usually like to do things step by step and if not I go over things ten times and over think the variables too much.

I would love to see a dyno or street video when its done that's for sure!
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The 365whp/685wtq wasn't my truck, that was NMB2(Justin Wheeler)'s truck. He did that with 130cc's of fuel. That same day, my truck, which had the same combo above in the 235/477 numbers, accept for a 160cc pump at that time knocked out 342whp/759wtq, but my clutch wasn't holding and I had some fueling issues of some sort, both of those numbers peaked at 2100rpm, so I don't like to use those numbers when calculating, that's why they weren't mentioned. That being said, that was 2 years ago. Last November I built my 6.9, and originally it was supposed to showcase all my parts, I built my 190cc pump, and originally was running an Aurora 3000 on the factory IDIT turbo hotside, it was to show how streetable a "big" pump IDI can be and to show how all the parts worked together. I sold the A3K to another guy and "upgraded" to a Batmo S259 that **** itself within the first 20 min, twice... After I got that sorted, I dropped an S366 on, and proceded to pop a HG... That was February... Looking back I felt I went the wrong direction with everything, and while it all worked good, It left me wanting more. I was going to do a bit more work to my 190 (Lock out the timing, blast it with some inlet pressure, get some more higher end fueling out of it) and run compounds, but I started getting burned out. I was looking at my PPump sitting on the shelf, and decided it was time to step up and save the smaller pumps for another project. That being said, Ive sold off all my other turbos, so Im going to be buying new. I think the GTX Ball bearing stuff is going to be out of my price range, Im already dumping a bunch of cash into the pump with a new cam and whatnot, and that took a bit more out of my budget. Im thinking between the fueling curve of the pump (Flat 300+cc's@4000rpm), If I drop a box unit 480/96/1.0 or 1.1 with a T4 housing, Drop a Diverter valve on it, and Gate it to 50psi, That should give me my 600whp by 3700RPM, and 850ft/lbs of torque. The bottom end can handle 850wtq no issue. If I gate the turbo to 50psi, that will keep it about 69% efficient at 113lbs/min.

Right now I think this is where I should start, if its a totally different animal after I get it running, then I guess back to the drawing board, but at least I will have some info to go off of.
 
I think the P-pump will make it a whole different animal, and you could probably get away with a BorgWarner 67.7 or something like that. If my memory rolodex is right, the 1,200hp Hypermax IDI that was built back in the day ran the pre-chambers and stock style injectors still, and had no issue turning 5,000rpm or making gobs of power.
 
JQmile said:
I think the P-pump will make it a whole different animal, and you could probably get away with a BorgWarner 67.7 or something like that. If my memory rolodex is right, the 1,200hp Hypermax IDI that was built back in the day ran the pre-chambers and stock style injectors still, and had no issue turning 5,000rpm or making gobs of power.
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I don't know, we will see. I will say this, using my numbers from my dyno where I did 342/759@2100, it managed to squeak out closer to 7lbs/min/HP based off of my boost numbers... but I haven't figured how to factor that into the mix, or even if I should.

That being said, as far as the hypermax truck is concerned, I've been clear of my skepticism of its said numbers. I don't like tooting my horn, but between Wheeler and myself, we have unleashed a bunch of info over the last few years just by pushing this platform. The part that makes me skeptical, is the fact that all the hard evidence that we have discovered, doesn't jive with the hearsay of the Hmax truck. It obviously made a ton of power (relatively of course) but I'm one in the camp of it making significantly lower numbers... The biggest issue I have with the truck, is there is no actual info at all on it, including from Hmax themselves, and its not because they are hiding the info, they just don't know. My goal with the IDI has been to document the whole process of making power with this engine, and this is the next step. People can drool over the Hmax truck all they want, but its reality is really only about 10 pictures and and a bunch of "he" said. If I can make this work I will consider it much more of a success than the Hmax truck.

That being said... Jason, I have the details somewhere in my archives, but the truck you did the wg/single/diverter on in hopes it would perform like a compound truck, was that a 12v? I can't remember...
 
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I did a bit more calculating using the numbers from my later dyno run that I haven't been using because I felt they were skewed. I came to the realization that they are accurate up to the points where the power and torque drops off, so it would still be fine to use those numbers up to that point.

That being the case, I was seeing 29-30psi on the dyno at that point, which puts me in at just over 7lb/min per HP airflow at 2100rpm. The other end of that equation is that I was also seeing 2.1hp/cc which is significantly lower than normal HP peak (More fuel). With these numbers, its apparent that the above is correct, in that the more fuel you have a available for a said amount of airflow, the Lb/min per Hp number rises. So in otherwords, if I run an appropriate AFR, its going to use the air I do have more effectively... So If I size the turbo a little smaller (S471/475, possibly even an S468) I could raise the "lb/min per HP" by adding a bit more fuel, which is something I haven't had the luxury of before.

With that being said, things aren't looking as absurd now as far as turbo sizing... Not as absurd as somebody sizing a turbo for a rotary pump anyway...
 
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